Is it safe to give a child an immunization when he's already sick with strep throat?

Probably: Immunizing when sick does not generally cause a serious problem with the illness. The question is whether the vaccine works as well when the immune system has already been stimulated by the infection.

Comfort level: I would suggest waiting if there is a fever. It is more comfortable for your child, if they are otherwise well before receiving their vaccinations.

Usually fine: Immunizations are often given during simple illness like strep to avoid loss of the opportunity. Most will never interfere with the treatment and the body is fully capable of a normal immune response at the time.